The present invention relates to an interface module and method thereof, and more particularly, to an interface module and method thereof capable of reducing noise, common-mode voltage, radiation of the interface module.
With the recent advances in wireless communication technology, Giga-bits wireless communication is visible and be required. Thus, an interface module between a wireless local area network (WLAN) card and a host device (e.g. a laptop, a personal computer) also needs to be capable of accomplishing high speed data transmission between the WLAN card and the host device. Thus, the interface module between the WLAN card and the host device may follow USB 3.0 standard, for achieving the high speed data transmission.
Please refer to FIG. 1A and FIG. 1B, which are schematic diagrams of a conventional interface module 10. The interface module 10 is realized under USB 3.0 standard, for transmitting data between a host device COM1 and a wireless device COM2. As shown in FIG. 1A and FIG. 1B, the interface module 10 comprises a connector 100 and a control circuit 102. The connector 100 is covered in a case 104 with a depth N and is utilized for plugging in the host device, to connect to the host device COM1. As is known, the case 104 is a metal plug shell, for shielding the metal contacts of the connector 100, and the metal plug shell is connected securely to ground at the host device when the connector plugs into the host device. The connector 100 is coupled to the control circuit 102 through a plurality of pin elements PIN. For controlling data transmission of the interface module 10, the control circuit 102 is not only coupled to the connector 100 but also configured in the same board of the wireless device COM2.
In order to be compatible with the USB 2.0, the USB 3.0 connector structure is fixed. However, the other five pin elements are added in the original connector space. Then, crowded, bent and non-impedance controlled pins let the interface module 10 emits noise, common-mode voltage, radiations when the interface module 10 transmits data with the high transmission speed of USB 3.0. The noise radiation generated while transmitting data covers the signal frequency band of the wireless device COM2, and thus, the performance of the wireless device COM2 would be decreased. In other words, if the interface module 10 transmits data in the transmission speed of USB 3.0, the sensitivity of the wireless device COM2 is degraded and the wireless device COM2 may work abnormally.
Besides, the well-known design rule of differential line, GSSG, can not be implemented in USB 3.0 pin sequence of the plurality of pin elements PIN. For example, the pin sequence of the plurality of pin elements PIN may only have a ground line between two pairs of signal lines. Thus, the impedances of the signal lines are imbalanced. Accordingly, the asymmetrical pin sequence not only degrades the common mode performance of the interface module 10, but also results in great noise radiation and crosstalk. Furthermore, the high speed transmission of USB 3.0 causes more return-current loops and results in a voltage difference between the connector 100 and ground of the host device COM1. The voltage difference between the connector 100 and the ground of the host device COM1 would also degrade the common mode performance of the interface module 10 and further result in greater noise radiation.
As can be seen from the above, the noise radiation generated when the interface module transmits data in the transmission speed of USB 3.0 would damage the performance of the wireless device and may result the wireless device works abnormally. Thus, how to reduce the noise radiation of the interface module realized in USB 3.0 for the wireless device becomes an important issue of the industry.